<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<style>
    .box {
        width: 500px;
        height: 400px;
        margin: 40px auto;
        background-color: #2b92d4;
        border-radius:100%;
        box-shadow: 0, 1px, 2px rgba(0, 0, 0, .3);
        animation: breathe 2s ease-in-out infinite alternate;
    }

    @keyframes breathe{
        0%{
            opacity:0.2;
            box-shadow: 0,1px,2px rgba(255,255,255,0.1);
        }
        50%{
            opacity:0.5;
            box-shadow: 0,1px,2px rgba(18,190,84,0.76);
        }
        100%{
            opacity:1;
            box-shadow: 0,1px,30px rgba(59,255,255,1);
        }
    }
</style>

<body>
    <!-- 呼吸效果 -->

    <div class="box"></div>
</body>

</html>